Process for preparing lubricating oils



Aug. 17, 1943. G. H. VON FUCHS 2,327,158

PROCESS FOR PREPARING LUBRICATING OILS Filed March 3, 1941 nuhzs I I o I2.5 5 1.5 10 Conczmmfion (KW) of Added Resins in Ftnon BkndlnvznforsrGzorqz Hugo von Fuchs Hqman Diamon Patented Aug. 17, 1943George Hugo von Fuchs and Hyman Diamond,

Alton, Ill., assignors to Shell Development Com- Dany, San Francisco,-

Delaware Calili, .a corporation of Application March 3, 1941; Serial No.381,530

9 Claims.

This invention relates to a new method for processing mineral oils to'produce lubricating oils of high stability, and more-particularly dealswith a method wherein lubricating oil stocks are fractionated andreblended according to a novel procedure. a v

The main purpose of this invention is to fractionate mineral lubricatingoil stocks ina manher so that onreblending the several fractions, notonly the viscosity of the blend can be controlled but within limits itsoxidation stability as well,

It is common practice in the manufacture of lubricating oils to divideavailable lubricating oil stocks by. fractional distillation into.so-called neutral oils and bright stocks, i. e., residual oils, andthereafter producing oils of different viscosities by blending two ormore of these frac-.

tions with each other in the necessary proportions to obtain whateverviscosity may be desirable. Thus relatively light oils as the SAE 10 and2D grades normally comprisepredominating amounts or consist of neutraloils, while the heavier grades contain as a rule more bright stock. 1

Now we have discovered thatlubricating oils of different viscositiesproduced by blending given neutrals and bright stocks in differentproportions have different oxidation stabilities. In the case ofwell-refined oils We have. found that as a rule intermediate-viscositygrades c'ontain-,

ing substantial portion of both neutrals and bright stocks, have thehighest stabilities. We have concluded that the reasonfor this peculiarbehavior is caused by a component which is normally contained in brightstocks in varyina amounts, namely, the bright stock resins. Bright stockresins as herein defined arehigh-boiling normal constituents of brightstocks. They are recognized by their ability of being adsorbed by silicagel and other acid solid adsorbents but are less readily adsorbed byalkaline or non-acidic adsorbents such as fullers earth, bauxite,zeolites, etc.

It ha been known for some time that highboiling mineral oils containresins, and that an approximate'analytical method for determining theircontent has been described by Kalichevsky and Fulton in NationalPetroleum News. volume 23, Number 51, pages 33-6, 1931. It washeretofore generally believed that these resins form a more or lessundesirable portion of lubricating oil being responsible for high carbonresidue of lubricating oils. Therefore, considerable efforts have beenexpended in the past to find methods for deresining lubricating oils, inthe hope of thereby reducing carbon residues. However, ap-

parently it remainedunnoticed that these resins have a verylstronginfluence on the oxidation stabilities of the oils, which influence maybe. beneficial or detrimental depending upon the concentration of theresins in the oil and on the, susceptibility of the particular oil to.the resins.

We have definitely established that any wellrefined mineral lubricatingoil should contain a certain amount of resins for maximum stability.

What this'amount should be cannotbe stated; in general terms because ofseveral diiiiculties.

In the first place, it appears that the group of. substances known asresins is-rather complex and apparently contains components some ofwhich are efiective in, smaller concentrations than others. Moreover, inthe usual processes of isolating or concentrating resins, resin concenetrates are obtained which besides the resinsnor mally contain harmfulimpurities. These impurities actually may cause a decrease in thestability of blends containing otherwise an optimum quantity of thebeneficial resins. Again different oils have vastly differentsusceptibili ties towards .the resins' Thus some oils may tolerate ornecessitate relatively large amounts of resins, While others reach theirmaximum. stabilities at much lower concentrations; fur- V therdifliculty, resides in the inaccuracy'of the analytical method, whichnot only fails to give close checks between duplicate determinations,but also fail to distinguish. between the useful resins and certaininert or harmful impurities. which normally are associated with theformer.

In View of the above, the only practical way of determining the optimumconcentration of in any one oil isto add successively larger amounts'cfresins to different samplesof this oil and then determine the oxidationstability of the several blends so obtained by any of the acceptedoxidation methods, preferably in the presence of iron. against theamount of resins or resin concentrate. added, the optimum blend istheneasily estab lished. v

Havingorice recognized that the presence of resins in limited amounts inlubricating oilshas definite advantages, our procedure of controllingboth the viscosities and. the stabilities of lubrieating oils, resolvesitself into producing besidesthe conventional neutral oils at leasttwohigh viscosity stocks, one of which i a bright stock, of low resincontent and. the other is a resin con centrate. Our improved-oils arethen produced;

By plotting the stabilities so obtained normally produced by blendingneutral oil, lowresin content bright stock and resin concentrate insuitable proportions.

While, as previously pointed out, the most deirable amount of resins to.be added cannot be predicted but must be established experimentally forlubricating oils from different sources, .we

find that the optimum resin contents normally vary between about 1% to10%, and more often than not between about 3% and "7%.

Bright stocks of low resin content and resin concentrates are mostreadily obtained by treating conventional bright stocks such as properlydeasphalted '(and de'waxed, if necessary) heavy mineral oil distillationresidues with normally gaseous hydrocarbons at elevated pressures,preferably at pressures and temperatures near or above the criticalconditions of these light hydrocarbons.

critical conditions. v

The operation 'of deresining is well known in the art of "lubricatingoil manufacture. ,Two fractions are thereby obtained, a bright stock oflow resin content and a resin concentrate. As a rule, both the deresinedbright stock and the"resin concentrate have lower oxidation stabilitie'sthan the bright stock fromwhich they are derived.

Bright stocks from which the resin concentrate's are obtainable may beproduced by any c'onventionalmethod of manufacture, such as topping acrude petroleum oil containing lubricating oil stock to produce aresidue having a suitable viscosity and removing asphalts (and waxes, ifnecessary) as by propane precipita-' tion or other known means.Vacuum-distilled heavy oils normally yield relatively small amounts ofresins, In fact the natural resin content of such oils is normally lowerthan is required for optimum stability. They may, however, be used inplace of the low-resin bright stock in making up blends.

The effectiveness of the resins as oxidation stabiliz rs may beconsiderably improved by removing therefrom certain impurities which arenormally associated therewith. We have discovered that harmfulimpurities can effectively be separated from the desirable resins bytreating the precipitated resin mixture or the resin concentrate with aneutral or alkaline-reacting adsorbent such as bauxite, brucite, basicpermutites, naturally 'a'ctive decolorizing clays as Florida clay andAttapulgus clay, fullers earth, etc. These adsorbents peculiarly enoughare selective for many of the impurities normally associated with theresins, but do not adsorb.

to any great extent the resins themselves. Therefore in our preferredprocedure we treat the resin concentrate preferably in solution in alow-boiling hydrocarbon oil such as naphtha,

fled by acid treatment. Moreover, because'resins' These conditions areknown as paraare susceptible to attack by sulfuric acid, it is notdesirable to treat bright stocks from which resins are to be separated,with excessive amounts of sulfuric acid. If for some reason severe acidtreatment of the bright stock is desired, this should be carried outafter the resins have been separated to avoid their being destroyed.

In order to illustrate our invention, reference is had to the attacheddrawing which represents a graph wherein concentration of resins invari- "ous lubricating oils of about the same viscosities is plottedagainst oxidation stability as measured by the time required to absorb1800 cc. of oxygen per 100 grams of oil by contacting the oil understandardized conditions with oxygen in the presence of iron (temperature313 F., 5 sq. cm. exposed iron surface per gram of oil, oxygen pressure760 mm. Hg). The oils were prepared by blending a (1) resin-free brightstock, (2) a neutral oil and (3) resins, to produce mixtures containing50% neutral and 50% mixed bright stock and resins, the ratio of brightstock to resins being different in the several mixtures. ,As will beseen from the drawing, a maximum stability is indicated at a resin content of about 5%.

Concerning the effects of impurities contained 7 in resins, thefollowing data are significant: A

comprising producing at least one low resin con tent mineral lubricatingoil and a petroleum 7 resin concentrate, purifying the latter withoutmaterially altering the resin content, and blendme said low resincontent oil with the purified resin concentrate, in an approximateproportion to produce a blend containing between 3 and '7 resin andhaving about maximum oxidation stability.

2. Process for manufacturing lubricating oils comprising producing atleast one low resin content mineral oil and a petroleum resinconcentrate, contacting the latter with. a basic reacting mineraladsorbent whereby acidic impurities are adsorbed without'materiallyaltering the resin content, and blending said low resin content oil withthe contacted resin concentrate in an approximate proportion to producea blend containing between 3 and 7% resin and having about maximumoxidation stability.

3. The process of claim 2 wherein said adsorbent is bauxite.

4. Process for manufacturing lubricating oil comprising producing atleast one low resin -content mineral lubricating oil and a petroleumresin concentrate, separately subjecting said low I resin content oil toa refining treatment to improve its oxidation stability, contacting saidresin concentrate with a basic reacting mineral adsorbent whereby acidicimpurities are adsorbed wlthoutmaterially altering the resin content,

7 and blending the treated low resin oil with the contacted resinconcentrate in an approximate proportion to produce a blend containingbetween 3 and 7% resin and having about maxi- 7. Process formanufacturing lubricating oil comprising subjecting a deasphaltedresidual lubricating oil stock of low wax content to a deresiningtreatment to produce a bright stock of lower resin content and a resinconcentrate,

purifying the latter without materially altering the resin content, andblending said bright stock with at least one neutral oil and said resinconcentrate in approximate proportions to produce the amount of resin insaid blend being between 3 and 7%.

8. The process of claim 7 wherein said deresining treatment comprisestreating the residual stock with a normally gaseous hydrocarbon underpara-critical conditions of said hydrocarbon.

9. Process for manufacturing lubricating oils comprising subjecting adeasphalted residual lubricating stock of low wax content to aderesining treatment to produce a bright stock of low resin content anda resin concentrate, separately subjecting said bright stock to arefining treatment capable of improving its oxidationstabilitmcontacting said resin concentrate with a basic reacting mineraladsorbent whereby acidic impurities are adsorbed without materiallyaltering the resin content, and blending the resulting refined low resinbright stock with at least one neutral oil and with the contacted resinconcentrate in approximate proportions to produce a blend containing 3and 7% resin and having about maximum oxidation stability.

GEORGE HUGO VON FUCHS. HYMAN DIAMOND.

a blend of about maximum oxidation resistance

